1. Field of the Invention
The present invention relates to a method of animating faces in three dimensions used in a data processing means including an engine for animating the head of a speaker previously stored and analyzed. For example, the data processing means relates to teleconferencing, teleworking or collaborative work, or intelligent agents for reading out pages of electronic mail, or virtual assistants with applications to e-commerce.
2. Description of the Prior Art
In the prior art, most animation engines are not muscular and the face is often animated by morphing between key expressions of the head produced manually by artists. Muscular animation engines are generally more comprehensive but do not take into account the elasticity of the skin, which rules out real time animation of the head.
A muscular animation engine is of interest because of the ease with which it can describe an animation as a set of muscular contractions, the head being structured in terms of predetermined sets of meshes, for example the lips, the eyes, the eyelids, etc. These sets of contractions can often be generalized from face to face. For example, a smile is always obtained by contraction of the zygomaticus muscles acting on the corners of the lips.
For example the following papers by Keith WATER: “A Muscle Model for Animating Three-Dimensional Facial Expression”, Computer Graphics, vol. 21, no. Jul. 4, 1987, pages 17-24, and “Analysis and Synthesis of Facial Image Sequences Using Physical and Anatomical Models”, IEEE Transactions on Pattern Analysis and Machine Intelligence, No. 6, pages 569 to 579, Jun. 15, 1993, suggest animating the face by means of muscle mobilization in the form of a vector within an angular influence sector within which a mesh node is moved as a function of an angular attenuation factor and a radial attenuation factor.
However, in the above type of animation engine, the lips are dissociated and the mouth is opened by rotation of the lower jaw fastened to the lower lip. This rotation destroys the corners of the lips, which does not reflect accurately the independent movement of the lips when speaking.